This invention relates to a system for controlling a power take-off clutch used in a transmission. More particularly, the invention is directed to a method and system for controlling a power take-off clutch that modulates a clutch pressure.
A power take-off (PTO) clutch is often used in an agricultural vehicle, such as, for example, a tractor, to provide power to its implements. The vehicle is powered by a motor or an engine, and equipped with a transmission having gear elements. Generally, a PTO clutch is located in the transmission to transmit torque from the motor to the implements, and engageable to transfer the torque from the motor to the implement through the clutch. The engagement of the clutch require precise timing to achieve smooth and high quality operation of the vehicle.
For example, U.S. Pat. No. 5,467,854 discloses a method of controlling a clutch-to-clutch shift for a transmission. The transmission includes a plurality of clutches, pressure control valves individually connected to the clutches, and an electronic control module. The control module receives a gear selection signal and responsively controls the operation of the pressure control valves. The shift operation of the transmission includes a modulation phase to gradually increase a clutch pressure to cause a desired decrease in clutch slip.
A PTO clutch, however, may face an unique problem because the PTO clutch is often operated under a wide range of implement loads. It is difficult to achieve precise timing of the PTO clutch engagement partly because the inertia of the implements can vary significantly. For example, a tractor pulling a combine or a mower endures higher inertia than one operating without an implement. The clutch engagement timing for low implement inertia or load may substantially differ from that for high implement inertia or load. As a result, it is difficult to operate a PTO clutch smoothly.
To solve this problem, a PTO clutch control system may be equipped with multiple clutch engagement timing settings. In the vehicle with multiple or alternative PTO clutch settings, an operator is required to manually select one of the clutch engagement timing settings based on the anticipated implement load. When the vehicle is subject to a different load, the operator accordingly selects the suitable setting. Such a system, however, does not fully accommodate load variation during operation of the implement. Moreover, changing settings during operation is inconvenient.
The present invention provides a PTO clutch control system allowing high quality operation overcoming one or more of the problems as set forth above.
In one aspect of the invention, a method is provided for controlling a PTO clutch of a transmission subject to a varying inertial load. The method includes providing a signal to a pressure control valve selectively engaged with the PTO clutch configured to engage a drive source of the transmission with an implement. The signal to the pressure control valve is modulated based on a single predetermined profile.
In another embodiment, a power take-off clutch control system for controlling a PTO clutch is provided. The control system includes a pressure control valve to actuate the clutch, and a control unit in communication with the pressure control valve. An input signal to the pressure control valve tracks a single predetermined profile.
In yet another embodiment, a vehicle is provided with a motor, a transmission coupled to the motor and having a PTO clutch, a pressure control valve coupled to the clutch to actuate the clutch, and a control unit coupled to the pressure control valve for providing a signal to the pressure control valve. The signal includes a single profile modulation signal to control clutch pressure over a varying load. A drive train is coupled to the transmission.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed